Construction of sparking plugs for internal-combustion engines



G. H. NEGUS. CONSTRUCTION OF SPARKING PLUGS FOR INTERNAL COMBUSTION ENGINES.

APPLICAT ON FILED JUNE 16, 1920. 1,364,787.. Patented Jan. 4, 1921.

UNITED STATES PATENT OFFICE.

GEORGE HENRY NEGUS, OF ROMFORD, ENGLAND.

Application filed June 16,

To all whom it may concern:

Be it known that I, GEORGE HENRY N EGUS, a subject of the King of (Jrreat Britain, residing at Romford, Essex, England, have mvented certain new and useful Improvements in Construction of Sparking Plugs for Internal-Combustion Engines, of which the following is a specification.

This invention relates generally to improvements in sparking plugs employing a thin wrapping of mica around a conical central electrode and supported by mica washers, the two mediums being combined to form the insulator, and the object of my invention is to construct a sparking plug having for insulation a thick mica cartridge, so made and held in its body that the use of mica washers may be dispensed with. This cartridge is composed of many laminations of mica sheet formed around the stem of the spark plug and is an improvement upon plugs made as above wherein mica washers are used as an auxiliary to the prime insulator viz., sheet mica wrapped. e use of my cartridge also allOWS a double chamber thus providing a greater path of high electrical resistance as the plug becomes foul, giving considerably longer life to the plug.

In combination with the construction of the cartridge is the manner in which it is held, providing virtually a homogeneous seal to varying temperatures and compression in the manner of a valve.

According to this invention the sparking plug body is constructed as shown on the annexed drawings in which Figure 1 a sectional elevation and Fig. 2 a plan View. The tubular casing A is formed from a solid hexagon bar in steel or gun metal formed on the outside with grooves B, B for cooling urposes and screw-threaded at lower end 5 with standard threads. Beyond this threaded portion is a reduced plain surface D extended a little distance to take a baffle ring E internally and carry the earth electrode F referred to later.

The formation of the inside of body A is cylindrical as at C for some distance from the bottom, the remaining height H being shaped conical.

Inside the body A is fitted mica sheet of many laminations of tubular section rolled very closely together to form a thick walled cartridge I, this being secured from being Specification of Letters Patent.

Patented Jan. 4. 1921.

1920. Serial No. 389,454.

unwound by a brass sleeve J which encircles same.

On the inside of this cartridge I is pushed a stem of metal formed on its lower end K with a cone of an angle to correspond with the conical portion H of the inside of body At the other end of this stem is a screw L to accommodate a locking nut M and terminal nut N. The lower end of this stem is provided with a small hole to receive a nickel pin P which forms the central and insulated electrode. Q is a steatite or like cover engaging the casing A and surrounding the stem K, L and a portion of the cartridge I to prevent the exposed portion of the cartridge I being rubbed or damaged.

In assembling the components already mentioned the central electrode P with itsstem K, L is pushed home first in the mica cartridge I leaving a certain length of the nickel pin P protruding downward, these components together with a brass gland J which surrounds the collar J are all inserted loosely in the body of casing A. Then with press tools of exact proportion the whole contents are cal inside H of casing A and at a certain depth the tools leave the cartridge I and stem K, L in the required position. By means of a combination of tools the brass gland J (which is now between the inner wall of the metal body and the outer wall of the sleeve J surrounding the cartridge) is rammed home and on its way is formed into a conical member, which grips the mica cartridge I thus making virtually an homo geneous seal between them'and body as will be understood from Fig. 1.

his arrangement makes it impossible for the high compression of the engine to leak and tightens rather than loosens with varying temperature and compression. The brass gland J has now traveled on the cartridge, leaving around the lower wall a chamber R which provides a path of high resistance should the plug become foul with soot or oil.

The stem K, L is now pushed up into the interior of the cartridge I high enough to leave a clear non-conducting chamber s about one third of the total length of the cartridge, which also provides a further path of high resistance to the current in the event of the plug becoming foul.

The bafiie ring E is now pushed snug up pressed hard up upon the coni-.

in the base of easing A and the nickel pin F pressed tight through a hole in the base D and through a hole in the baflle ring F, as shown, thereby securing it from moving. This nickel pin F serves also as the earth electrode and is placed over in front or at the side of the central electrode point. This method gives very long life to the plug which rarely requires cleaning, but should this be necessary all that is required is to remove the cross pin F and the baffle E when a little kerosene on a brush readily accomplishes the necessary cleaning.

What I do claim as my invention and desire to secure by Letters Patent, is z- 1. A sparking plug for internal combustion engines, comprising a tubular casing or body having its inside wall formed with a conical portion, a tubular insulator formed from sheet mica of many laminations, a sleeve surrounding the insulator tube, a stem formed with a conical portion and carrying a pin forming the central electrode engaging the inside of the tubular insulator, a baflie ring and earth electrode, locking and terminal nutsengaging the stem, an insuews? lating cover, and a gland encircling the sleeve on the insulator, the stem, and its electrode, said insulator being securely held in the plug casing or body by the gland, substantially as described.

2. A sparking plug for internal combustion engines, comprising a tubular casing having the inner wall thereof formed with a conical portion, a tubular insulator, a sleeve surrounding said insulator, a central electrode formed with an intermediate conical portion located within the insulator, an

electrode contacting with said casing and arranged in operative relation to said central electrode, a gland embracing said sleeve adapted to be pressed between the conical portion of said casing and said sleeve for securely holding said insulator in proper position within the casin In testimony whereof have hereunto set my hand in presence of two subscribing Witnesses.

GEORGE HENRY NEGUS. lVitnesses FRED NORTHRUP, J. M. LIVENS. 

